Alert archive / Iowa / Mesoscale Discussions in 2009

Mesoscale Discussion 1817

August 7, 200941 counties in Iowa; 21 counties in Minnesota

The Storm Prediction Center issued this mesoscale discussion at Aug 7, 2009, 8:58 PM CDT for 41 counties in Iowa; 21 counties in Minnesota. It was in force for 92 min.

The area

The outline as issued.

The facts

Issued
Aug 7, 2009, 8:58 PM CDT (01:58 UTC)
Expired
Aug 7, 2009, 10:30 PM CDT
In force
92 min
Issued by
the Storm Prediction Center
All 62 counties

Black Hawk County, IA, Boone County, IA, Bremer County, IA, Buchanan County, IA, Buena Vista County, IA, Butler County, IA, Calhoun County, IA, Cerro Gordo County, IA, Cherokee County, IA, Chickasaw County, IA, Clay County, IA, Dickinson County, IA, Emmet County, IA, Fayette County, IA, Floyd County, IA, Franklin County, IA, Greene County, IA, Grundy County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Howard County, IA, Humboldt County, IA, Ida County, IA, Kossuth County, IA, Lyon County, IA, Marshall County, IA, Mitchell County, IA, O'Brien County, IA, Osceola County, IA, Palo Alto County, IA, Pocahontas County, IA, Polk County, IA, Sac County, IA, Story County, IA, Tama County, IA, Webster County, IA, Winnebago County, IA, Winneshiek County, IA, Worth County, IA, Wright County, IA, Blue Earth County, MN, Brown County, MN, Cottonwood County, MN, Dodge County, MN, Faribault County, MN, Fillmore County, MN, Freeborn County, MN, Jackson County, MN, Le Sueur County, MN, Martin County, MN, Mower County, MN, Murray County, MN, Nicollet County, MN, Nobles County, MN, Olmsted County, MN, Redwood County, MN, Rice County, MN, Sibley County, MN, Steele County, MN, Waseca County, MN, Watonwan County, MN

The radar

The Des Moines radar (KDMX), 163 km from the middle of the area, began a volume at 01:58 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Minneapolis, MN (KMPX), launched 00:00Z, 2.0 hours before the alert went out and 186 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Minneapolis, MN at 00:00Z on 2009-08-08Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1 joules per kilogram.LCLEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Minneapolis, MN at 00:00Z on 2009-08-08The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 183 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
1 J/kg
Mixed-layer CIN
0 J/kg
Mixed-layer LCL
517 m above ground
0-6 km bulk shear
43 kt
0-1 km storm-relative helicity
183 m²/s²
0-3 km storm-relative helicity
341 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.2

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 7, 10:14 PM CDTSevere Thunderstorm WatchSPCBlack Hawk, Boone, Bremer, Buena Vista, Butler, Calhoun and 27 more6 hr
Aug 8, 1:29 AM CDTMesoscale DiscussionSPCAllamakee, Benton, Black Hawk, Boone, Bremer, Buchanan and 37 more2 hr
Aug 8, 12:16 PM CDTMesoscale DiscussionSPCDickinson, Emmet, Lyon, Osceola29 min
Aug 8, 12:47 PM CDTTornado WatchSPCLyon, Osceola5 hr
Aug 8, 3:27 PM CDTMesoscale DiscussionSPCDickinson, Lyon, Osceola33 min
Aug 8, 9:29 AM CDTMesoscale DiscussionSPCAnoka, Brown, Carver, Dakota, Goodhue, Hennepin and 12 more91 min
Aug 8, 2:17 PM CDTMesoscale DiscussionSPCWilkin58 min
Aug 8, 3:46 PM CDTTornado WatchSPCAnoka, Benton, Blue Earth, Carver, Chisago, Dakota and 24 more8 hr
Aug 8, 5:36 PM CDTMesoscale DiscussionSPCAnoka, Benton, Blue Earth, Brown, Carver, Chisago and 26 more84 min

Nearby

Mesoscale Discussions in Iowa, 2009Mesoscale Discussions in Minnesota, 2009Every mesoscale discussion in 2009

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.